(a) Field of the Invention
The present invention relates to a device-to-device (D2D) communication system and a method for allocating resources and power using the same, and more particularly, to a D2D communication system and a method for allocating D2D resources and power to maximize spectral efficiency using the same in a cellular system for supporting D2D communication.
(b) Description of the Related Art
Recently, as various services using a wireless mobile communication system are provided, data traffic has drastically increased, and a device-to-device (D2D) communication in a cellular system is under research and development (R&D) and standardization to solve such a problem.
The D2D communication allows adjacent terminals to directly communicate each other without passing through infrastructure such as a base station and the like, thereby enabling a new service based on proximity and improving spectral efficiency of the cellular system at the same time.
Therefore, a D2D link needs to share an existing cellular frequency resource with a cellular link so as to improve spectral efficiency.
However, while the D2D link share the existing cellular frequency resource with the cellular link to improve the spectral efficiency, interference there between may occur.
As such, as a research is being carried out to allow the D2D communication and the cellular communication to use the same communication band, appropriate resource allocation and power distribution of the D2D communication has become a critical issue to reduce mutual interference between the D2D communication and the cellular communication.
In the most typical approach to allocating resources in the cellular link and the D2D link, the base station collects information about channel statuses of respective links and mutually interfered links, and then performs resource allocation based on the collected information.
Such an approach has a merit of correctly measuring influence of interference, but it is not desirable because an optimization issue such as increased complexity in measuring and collecting channel information, signaling overhead increase, and a complex resource allocation algorithm should be addressed.
In addition, in the case of a time-varying channel that varies at a very high speed, performance degradation may be a serious problem since it is difficult to obtain correct channel information.
Another aspect that is not considered in conventional resource allocation schemes is to determine which resources are effective to share with.
For example, it may be difficult to share a D2D link of a cellular user's resource near a cell edge because of severe interference.
Accordingly, the resource allocation algorithm needs to be designed such that it preferentially shares a resource with less interference.
Further, the existing cellular communication and the D2D communication have been considered as separate systems with respect to each other, so resource and power allocations for the cellular communication and the D2D communication are independently performed.
The background art of the present invention is disclosed in the Korean Patent Laid-Open Publication No. 2008-0028347 (laid-open on Mar. 31, 2008).